This invention relates generally to engines which are exposed to or partially submerged in water, and particularly to such an engine that includes a lubrication filler or drain plug which detects the presence of water in the lubricant within the engine and generates a visual signal in response thereto. While the present invention is particularly useful in marine engines which are partially submerged in water, it may also be used in other applications where the detection of water in a lubricant may be desirable.
In outboard or inboard-outboard marine engines, the propeller and its associated drive gears are collectively known as the drive unit and/or lower unit, and it is submerged in water during normal operation. Even though the units are equipped with seals and gaskets to keep out the surrounding water, the seals may become damaged or otherwise fail due to normal wear. This failure can allow water to enter the drive unit and become mixed with the lubricant contained therein. As a result of this contamination of the lubricant by water, the internal components of the drive unit, including its gears, bearings, and propeller shaft, are almost certain to be damaged or destroyed if the condition is allowed to continue. The potential for destruction is hastened in engines used in a saltwater environment. Subsequent repair or replacement of the drive unit can be costly.
Typically, the units include two plugged openings. The first plugged opening is located adjacent the top of the unit and is used as a vent in the adding or draining of lubricant thereto. The other plugged opening is located adjacent the base of the unit and is used to fill the unit and to drain lubricant therefrom. One known method of determining whether water has become mixed with the lubricant in an drive unit is to drain the oil therefrom and examine the oil for presence of water. Water mixed with gear drive lubricant will give the lubricant a milky appearance as opposed to the normal dark appearance of uncontaminated lubricant.
An alternate method of detecting the presence of water in outdrive lubricant is provided by Haynes U.S. Pat. No. 4,757,710 which discloses a sight glass fitted into a hole formed in the side of the drive unit casing. This sight glass allows the visual inspection of the outdrive lubricant without removing the lubricant from the drive unit. The sight glass of Haynes is basically a window. A second Haynes patent, U.S. Pat. No. 4,803,876 discloses the same sight glass as the previous Haynes patent, but the second Haynes sight glass is directed toward manufacturers of drive units in that it requires a hole to be specially formed in the side of the casing of the drive unit during manufacture. Wicklein U.S. Pat. No. 4,789,363, incorporates the sight glass principle of Haynes into a unit more readily adapted to existing marine engines in that the sight glass of Wicklein is configured to replace the aforementioned drain plug on the drive unit.
The sight glass units of the above-mentioned patents allow boating enthusiasts to inspect the condition of the lubricant in the drive unit without draining the lubricant therefrom, making the inspection easier, yet less reliable than draining the lubricant for inspection. The boater still has to make a visual inspection of the lubricant itself and then make a determination, based on the color of the lubricant, whether the lubricant has become fouled by the incursion of water into the drive unit. However, this visual inspection surveys only a very small portion of the outdrive lubricant, namely that which is in contact with the sight glass at the time of inspection. The present state of the art allows at best a rough approximation of the water content, if any, of the gear lubricant in the drive unit of a marine engine.
While these concerns are of particular interest to boating enthusiasts, similar problems may arise in an automotive environment or in other lubricant containing devices which are exposed to water or moisture.